Endocrinology of year-round reproduction in a highly seasonal habitat: environmental variability in testosterone and glucocorticoids in baboon males - PubMed (original) (raw)

Endocrinology of year-round reproduction in a highly seasonal habitat: environmental variability in testosterone and glucocorticoids in baboon males

Laurence R Gesquiere et al. Am J Phys Anthropol. 2011 Feb.

Abstract

In conditions characterized by energetic constraints, such as in periods of low food availability, some trade-offs between reproduction and self-maintenance may be necessary; even year-round breeders may then be forced to exhibit some reproductive seasonality. Prior research has largely focused on female reproduction and physiology, and few studies have evaluated the impact of environmental factors on males. Here we assessed the effects of season and ambient temperatures on fecal glucocorticoid (fGC) and testosterone (fT) levels in male baboons in Amboseli, Kenya. The Amboseli basin is a highly challenging, semiarid tropical habitat that is characterized by strongly seasonal patterns of rainfall and by high ambient temperatures. We previously reported that female baboons were impacted by these challenging environmental conditions. We ask here whether male baboons in the same environment and groups as females exhibit similar physiological effects. We found that after accounting for male age and individual variability, males exhibited higher fGC levels and lower fT levels during the dry season than during the wet season. Furthermore, fT but not fGC levels were lower in months of high average daily maximum temperatures, suggesting a direct impact of heat on testes. Our results demonstrate that male baboons, like females, experience ecological stress that alters their reproductive physiology. The impact of the environment on male reproduction deserves more attention both in its own right and because alteration in male physiology may contribute to the reduction in female fertility observed inchallenging environments.

2010 Wiley-Liss, Inc.

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Figures

Figure 1

Figure 1

Differences in fGC and fT concentrations in (a) wet vs. dry se ason and (b) cool vs. hot months. The y axis represents the residual fGC or fT values obtained from the GLMM, which included all the predictors listed above in Table 1 except for the variable of interest (see Methods). Each value represents the mean ± SE across male monthly averages. N represents the number of monthly averages. Statistical significance was determined using the Mann Whitney U.

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